Evidence suggests that multiple sclerosis (MS) is caused by host genetic factors in association with one or more environmental agents. The clinical and pathological features of MS implicate viral infections as either cofactors in its aetiology or triggers of relapses, although no specific environmental factors have been identified. In particular, several herpesviruses have attracted interest because their ability to cause latent infections that periodically reactivate has some familiarity with the relapsing-remitting course of MS. Further, most human herpesviruses can be readily found within the central nervous system and several are known to be capable of inducing demyelination, both in humans and in experimentally infected animals. This brief review takes a systematic look at reported associations between herpesviruses and MS and suggests some criteria that must be met in further studies. One of the greatest challenges in confirming or refuting a role for herpesviruses in chronic diseases is their ubiquitous nature. It is stated from the outset that the associations described here remain controversial.